Interspinous implants and methods for implanting same

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to the following applications: U.S. patent application Ser. No. 11/743,086, filed May 1, 2007; U.S. Provisional Patent Application No. 60/959,799, filed Jul. 16, 2007; U.S. Provisional Patent Application No. 60/961,780, filed Jul. 24, 2007; U.S. Provisional Patent Application No. 61/000,831, filed Oct. 29, 2007; and U.S. Provisional Patent Application No. 61/001,430, filed Nov. 1, 2007, each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention is directed to spinal implants, and more particularly, to an interspinous implant with deployable wings for treating lumbar spinal stenosis, methods for the percutaneous implantation of the interspinous implant, and techniques for determining an appropriate size of the interspinous implant.

2. Description of Related Art

The spine consists of a column of twenty-four vertebrae that extend from the skull to the hips. Discs of soft tissue are disposed between adjacent vertebrae. The vertebrae provide support for the head and body, while the discs act as cushions. In addition, the spine encloses and protects the spinal cord, which is surrounded by a bony channel called the spinal canal. There is normally a space between the spinal cord and the borders of the spinal canal so that the spinal cord and the nerves associated therewith are not pinched.

Over time, the ligaments and bone that surround the spinal canal can thicken and harden, resulting in a narrowing of the spinal canal and compression of the spinal cord. This condition is called spinal stenosis, which results in pain and numbness in the back and legs, weakness and/or a loss of balance. These symptoms often increase after walking or standing for a period of time.

There are number of non-surgical treatments of stenosis. These include non-steroidal anti-inflammatory drugs to reduce the swelling and pain, and corticosteroid injections to reduce swelling and treat acute pain. While some patients may experience relief from symptoms of spinal stenosis with such treatments, many do not, and thus turn to surgical treatment. The most common surgical procedure for treating spinal stenosis is decompressive laminectomy, which involves removal of parts of the vertebrae. The goal of the procedure is to relieve pressure on the spinal cord and nerves by increasing the area of the spinal canal.

Interspinous process decompression (IPD) is a less invasive surgical procedure for treating spinal stenosis. With IPD surgery, there is no removal of bone or soft tissue. Instead, an implant or spacer device is positioned behind the spinal cord between the spinous process that protrudes from the vertebrae in the lower back. A well-known implant used for performing IPD surgery is the X-STOP® device, which was first introduced by St. Francis Medical Technologies, Inc. of Alameda Calif. However, implantation of the X-STOP® device still requires an incision to access the spinal column to deploy the X-STOP® device.

It would be advantageous to provide an implant for performing IPD procedures that could be percutanously inserted into the interspinous space and effectively treat lumbar spinal stenosis.

SUMMARY OF THE INVENTION

The subject invention is directed to a spinal implant used primarily for interspinous process decompression procedures that can be percutaneously introduced into the interspinous space. In its most basic configuration, the device includes a body portion having an interior cavity, a plurality of locking wings adapted and configured to move between a stowed position retracted within the interior cavity of the body portion and a deployed position extended from the interior cavity of the body portion, and means for moving the plurality of locking wings from the stowed position to the deployed position.

The subject invention is also directed to a method of percutaneously placing a spinal implant during an interspinous process decompression procedure, which includes, among others, the steps of providing a spinal implant having a body portion containing a plurality of deployable locking wings that are dimensioned and configured to engage the spinous processes of adjacent vertebrae at symptomatic disc levels, advancing a curved stylet through the skin from one side of the spine down into the spinous processes between the symptomatic disc levels, guiding the spinal implant along the path defined by the curved stylet into the spinous processes from a unilateral approach, and subsequently deploying the locking wings to engage the spinous processes of adjacent vertebrae.

The subject invention is further directed to a method of percutaneously placing a spinal implant that includes the steps of providing a spinal implant having a body portion containing a plurality of deployable locking wings dimensioned and configured to engage the spinous processes of adjacent vertebrae at symptomatic disc levels, advancing a curved stylet through the skin from one side of the spine, down into the spinous process between the symptomatic disc levels and out through the skin on the opposite side of the spine, so as to enable a bilateral approach to the spinous process. The method further includes the steps of guiding the spinal implant along the path defined by the curved stylet into the spinous processes from either side of the spine and subsequently deploying the locking wings to engage the spinous processes of adjacent vertebrae.

The implant may be advantageously used for various treatments including as an adjunct to a fusion, for treatment of back pain and as a treatment to alleviate symptoms of a protruding lumbar disc.

The subject invention is further directed to a tool kit for facilitating the percutaneous implantation of the device. The kit includes one or more of the following components: a stylet assembly having a graduated positioning stylet, a curved stylet and an adjustable bridging portion with curved guide sleeve for the curved stylet. The kit may further include a set of curved tubular dilators of varying diameter and a plurality of implants of varying size.

The subject invention is also directed to an apparatus for measuring the optimum size of an interspinous implant for treating lumbar spinal stenosis. The apparatus includes distracting means dimensioned and configured for percutaneous insertion into the interspinous space between adjacent spinous processes, wherein the distracting means is movable between a closed insertion position and an open distracting position. The apparatus further includes deployment means for moving the distracting means between the closed insertion position and the open detracting position, wherein an amount of movement of the deployment means corresponds to an optimum size of interspinous implant for placement in the interspinous space between the adjacent spinous processes.

The subject invention is also directed to a method for measuring the optimum size of an interspinous implant for treating lumbar spinal stenosis. The method includes the step of percutaneously inserting distracting means into the interspinous space between adjacent spinous processes, wherein the distracting means is movable between a closed insertion position and an open distracting position. The method further includes the step of moving the distracting means between the closed insertion position and the open detracting position, and then correlating movement of the distracting means to an optimum size of interspinous implant for placement in the interspinous space between adjacent spinous processes.

In one embodiment, the subject technology is directed to an interspinous implant for placement between spinous processes of symptomatic disc levels including a shell having upper and lower shell portions defining four interior grooves that terminate in openings in the shell, the shell having a pawl adjacent each opening. Four deployable ratcheting locking wings slidably couple in a respective groove between: i) a stowed position in which the wings are within the grooves; and ii) a deployed position in which the wings extend outward from the shell. Each wing has a set of ratchet teeth for engaging and locking the respective pawl in the deployed position. A pair of coaxial locking wheels rotatably mount in the shell to selectively exert a force against each locking wing to move the locking wings from the stowed to the deployed position and a deployment cable couples to the wheels to actuate rotation of the wheels.

The implant may further have a guide on the shell for accommodating a stylet during a percutaneous placement procedure. Additionally, two wings may be located on first parallel, spaced apart geometric planes that extend on a first side of a centerline of the shell, with the other two wings are located on second parallel, spaced apart geometric planes that extend on a second side of the centerline of the shell. The interspinous implant may also include a placement tool for introducing the shell into the spinous process. The placement tool may include an elongated tubular stem having a straightened distal portion and a curved proximal portion that form a central lumen for accommodating the deployment cable and a coupling sleeve on the straightened distal portion for selectively engaging the shell. In another embodiment, the placement tool may be an elongated tubular stem that is curved.

The interspinous implant may also include a stylet assembly for percutaneous insertion of the interspinous implant. The stylet assembly includes an elongated graduated positioning stylet for setting a position of the stylet assembly over a central axis of a spine, a curved stylet for gaining lateral access to an interspinous space and an adjustable guide bridge having a central portion extending between the positioning stylet and the curved stylet for guiding the positioning stylet, the bridge also having a curved guide sleeve for guiding the curved stylet. The curved stylet may be sized and configured for a unilateral or bilateral insertion.

The interspinous implant may also include an actuating mechanism including an elongated, arcuate, hollow cable attachment device having a tapered distal end with radially inwardly extending flexible prongs that form a distal opening, a deployment cable having a distal end attached to the interspinous implant and a proximal end having a ball captured by the flexible prongs and a second tube for insertion into the cable attachment device to deflect the flexible prongs and, in turn, release the ball therefrom after deployment of the interspinous implant.

In another embodiment, the subject technology is directed to a method of placing a spinal implant comprising the steps of: providing a spinal implant having a body portion containing a plurality of deployable locking wings dimensioned and configured to engage the spinous processes of adjacent vertebrae at symptomatic disc levels; advancing a curved stylet through the skin from one side of the spine down into the spinous processes between the symptomatic disc levels; guiding the spinal implant along a path defined by the curved stylet into the spinous processes from a unilateral approach; and deploying the locking wings to engage the spinous processes of adjacent vertebrae.

In still one more embodiment, the subject technology is directed to a device for measuring percutaneously an optimum size of an interspinous implant. The measuring device includes a proximal deployment portion including a plunger tube carrying a rod, a distal measuring assembly including four connected arms pivotally connected at four coupling joints, a central shaft connected to the rod of the plunger tube a proximal end and connected to the coupling joint on a distal end and two opposed concave cradles adjacent opposed coupling joints adapted to engage a spine when the rod and, in turn, the central shaft is pulled in a proximal direction while the plunger tube remains stationary, so that the connected arms expand from a closed to a measuring position. The measuring device may also include a strain gauge operatively associated with the plunger tube and rod for determining a force to be applied by an interspinous implant.

In another embodiment, the measuring device includes an elongated body portion having a pair of jaw members at a distal end thereof for positioning in the interspinous space, a cradle on each jaw member, the cradles being adapted and configured to cup an adjacent spinous process, a plunger tube and a rod partially housed within the plunger tube and attached to the jaw members for selectively moving the jaw members from a closed position to an open position in which the cradles engage the spinous process, wherein a travel distance of the rod within the plunger tube correlates to a length to which an interspinous space was distracted.

The subject technology also includes a method for measuring the optimum size of an interspinous implant for treating lumbar spinal stenosis including the steps of percutaneously inserting distracting means into the interspinous space between adjacent spinous processes, wherein the distracting means is movable between a closed insertion position and an open distracting position, moving the distracting means between the closed insertion position and the open detracting position and correlating movement of the distracting means to an optimum size of interspinous implant for placement in the interspinous space between adjacent spinous processes.

It is to be understood that each feature of the disclosed implants and methods may be interchanged and coupled freely with the various other features to utilize any combination thereof. These and other features of the interspinous implant and percutaneous placement method of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiment taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the interspinous implant of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail hereinbelow with reference to certain figures, wherein:

<figref idrefs="DRAWINGS">FIG. 1</figref> is a perspective view of an interspinous implant in accordance with the subject invention, which includes a main shell portion having a plurality of locking wings and an insertion tool to facilitate percutaneous introduction of the implant into the spine;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a top plan view of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>, illustrating the locking wings in a deployed position;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a side elevational view of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a cross-sectional view taken along line <b>4</b>-<b>4</b> of <figref idrefs="DRAWINGS">FIG. 3</figref> illustrating a locking wheel disposed within the main shell of the interspinous implant for deploying a pair of opposed lock wings;

<figref idrefs="DRAWINGS">FIG. 5A</figref> is a detailed perspective view of the lower portion of the main shell of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 5B</figref> is a plan view of the inside of the lower portion of the main shell of <figref idrefs="DRAWINGS">FIG. 5A</figref>;

<figref idrefs="DRAWINGS">FIG. 5C</figref> is a side view of the inside of the lower portion of the main shell of <figref idrefs="DRAWINGS">FIG. 5A</figref>;

<figref idrefs="DRAWINGS">FIG. 5D</figref> is a proximal end view of the lower portion of the main shell of <figref idrefs="DRAWINGS">FIG. 5A</figref>;

<figref idrefs="DRAWINGS">FIG. 6A</figref> is a detailed perspective view of the upper portion of the main shell of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 6B</figref> is a plan view of the inside of the upper portion of the main shell of <figref idrefs="DRAWINGS">FIG. 6A</figref>;

<figref idrefs="DRAWINGS">FIG. 6C</figref> is a side view of the inside of the upper portion of the main shell of <figref idrefs="DRAWINGS">FIG. 6A</figref>;

<figref idrefs="DRAWINGS">FIG. 6D</figref> is another side view of the inside of the upper portion of the main shell of <figref idrefs="DRAWINGS">FIG. 6A</figref> with the inside shown in phantom lines;

<figref idrefs="DRAWINGS">FIG. 6E</figref> is a proximal end view of the upper portion of the main shell of <figref idrefs="DRAWINGS">FIG. 6A</figref>;

<figref idrefs="DRAWINGS">FIG. 6F</figref> is a distal end view of the upper portion of the main shell of <figref idrefs="DRAWINGS">FIG. 6A</figref>;

<figref idrefs="DRAWINGS">FIG. 7A</figref> is a detailed perspective view of a locking wing of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 7B</figref> is a side view of the locking wing of <figref idrefs="DRAWINGS">FIG. 7A</figref>;

<figref idrefs="DRAWINGS">FIG. 7C</figref> is a top view of the locking wing of <figref idrefs="DRAWINGS">FIG. 7A</figref>;

<figref idrefs="DRAWINGS">FIG. 7D</figref> is a bottom view of the locking wing of <figref idrefs="DRAWINGS">FIG. 7A</figref>;

<figref idrefs="DRAWINGS">FIG. 7E</figref> is an end view of the locking wing of <figref idrefs="DRAWINGS">FIG. 7A</figref>;

<figref idrefs="DRAWINGS">FIG. 8A</figref> is a detailed perspective view of a locking wheel of the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 8B</figref> is a top view of the locking wheel of <figref idrefs="DRAWINGS">FIG. 8A</figref>;

<figref idrefs="DRAWINGS">FIG. 8C</figref> is a side view of the locking wheel of <figref idrefs="DRAWINGS">FIG. 8A</figref>;

<figref idrefs="DRAWINGS">FIG. 8D</figref> is an end view of the locking wheel of <figref idrefs="DRAWINGS">FIG. 8A</figref>;

<figref idrefs="DRAWINGS">FIG. 8E</figref> is a detailed top view of another locking wheel and a portion of the actuating mechanism for use in the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 9A</figref> is a detailed perspective view of a placement tool for use with the interspinous implant of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 9B</figref> is a side view of the placement tool of <figref idrefs="DRAWINGS">FIG. 9A</figref>;

<figref idrefs="DRAWINGS">FIG. 9C</figref> is a top view of the placement tool of <figref idrefs="DRAWINGS">FIG. 9A</figref>;

<figref idrefs="DRAWINGS">FIG. 9D</figref> is a distal end view of the placement tool of <figref idrefs="DRAWINGS">FIG. 9A</figref>;

<figref idrefs="DRAWINGS">FIG. 10A</figref> is a perspective view of the interspinous implant of the subject invention, in cross-section to illustrate the four locking wings and two locking wheels in a stowed position;

<figref idrefs="DRAWINGS">FIG. 10B</figref> is a perspective view of the interspinous implant of the subject invention, in cross-section to illustrate the four locking wings and two locking wheels in a deployed position;

<figref idrefs="DRAWINGS">FIG. 11</figref> is a perspective view of the interspinous implant of the subject invention, with the four locking wings fully retracted and stowed within the shell of the device;

<figref idrefs="DRAWINGS">FIG. 12</figref> is an elevational view of the stylet assembly used to percutaneously deploy the interspinous implant of the subject invention;

<figref idrefs="DRAWINGS">FIGS. 13 through 16</figref> illustrate the percutaneous introduction of the interspinous implant of the subject invention by way of a unilateral approach from one side of the spine;

<figref idrefs="DRAWINGS">FIGS. 17 through 21</figref> illustrate the percutaneous introduction of the interspinous implant of the subject invention by way of a bilateral approach from either side of the spine;

<figref idrefs="DRAWINGS">FIG. 22</figref> is a perspective view of a placement or cable attachment device utilized in conjunction with the interspinous implant of the subject invention;

<figref idrefs="DRAWINGS">FIG. 23</figref> is a distal end view of the attachment device of <figref idrefs="DRAWINGS">FIG. 22</figref>;

<figref idrefs="DRAWINGS">FIG. 24</figref> is an illustration of an apparatus for measuring the optimum size of an interspinous implant, which is shown in an initial measuring position;

<figref idrefs="DRAWINGS">FIG. 25</figref> is an illustration of the apparatus shown in <figref idrefs="DRAWINGS">FIG. 24</figref> in an open or distracting position;

<figref idrefs="DRAWINGS">FIG. 26</figref> is an illustration of another apparatus for measuring the optimum size of an interspinous implant, which is shown in an insertion or closed position;

<figref idrefs="DRAWINGS">FIG. 27</figref> is an illustration of the apparatus shown in <figref idrefs="DRAWINGS">FIG. 26</figref> in an open or distracting position; and

<figref idrefs="DRAWINGS">FIG. 28</figref> is a top plan view of a tool kit for facilitating the percutaneous placement of a spinal implant.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention overcomes many of the prior art problems associated with implants to relieve spinal stenosis. The advantages, and other features of the system disclosed herein, will become more readily apparent to those having ordinary skill in the art from the following detailed description of certain preferred embodiments taken in conjunction with the drawings which set forth representative embodiments of the present invention and wherein like reference numerals identify similar structural elements. All relative descriptions herein such as horizontal, vertical, left, right, upper, and lower are with reference to the Figures, and not meant in a limiting sense. For reference, proximal is generally the area or portion adjacent or near the surgeon whereas distal refers to the portion remote or away from the surgeon.

Spinal Implant

Referring now <figref idrefs="DRAWINGS">FIG. 1</figref>, there is illustrated an interspinous implant constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral <b>10</b>. Implant <b>10</b> is particularly well adapted for use in performing minimally invasive surgical procedures for treating spinal stenosis, including, for example, interspinous process decompression (IPD).

It is envisioned however, that the implant <b>10</b> of the subject invention can be used in other spinal procedures as well, including, but not limited to as an adjunct to spinal fusion procedures. Those skilled in the art will readily appreciate from the following description that the interspinous implant of the subject invention is well adapted for percutaneous insertion, and thus overcomes many of the deficiencies of prior art devices presently used in IPD procedures. That is, the implant <b>10</b> is dimensioned and configured for introduction and placement through a small stab skin incision.

Referring to <figref idrefs="DRAWINGS">FIGS. 1 through 4</figref>, the interspinous implant <b>10</b> of the subject invention includes a main shell or body portion <b>12</b> having upper and lower shell portions <b>12</b><i>a</i>, <b>12</b><i>b</i>. The shell portions <b>12</b><i>a</i>, <b>12</b><i>b </i>may have an interference fit or be held together by a fastener (not shown) inserted in a threaded hole <b>44</b>. The shell portions <b>12</b><i>a</i>, <b>12</b><i>b </i>are preferably formed from a biocompatible polymeric material that has a modulus of elasticity that is substantially similar to that of bone, for example, polyetheretherketon thermoplastic (PEEK) or a similar material. The main shell <b>12</b> may also be made of a biocompatible metal such as a titanium alloy or like material. The main shell <b>12</b> is dimensioned and configured for placement between the spinous processes of symptomatic disc levels. (See also <figref idrefs="DRAWINGS">FIGS. 5A and 5B</figref>). Placement of the implant in this manner limits extension at the symptomatic levels, while preserving mobility and alignment. While the shell <b>12</b> has a generally bullet or frusto-conical shape, it is envisioned that the curved end section could be truncated or presented in a flattened orientation, whereby the shell would assume a barrel-shaped configuration among many other variations. The shell <b>12</b> has opposing depressions <b>13</b> that serve to match the profile of the adjacent bone when deployed.

The lower shell portion <b>12</b><i>b </i>includes an optional guide <b>15</b> for accommodating a stylet during a percutaneous placement procedure, as best seen in <figref idrefs="DRAWINGS">FIGS. 5A-5D</figref> and described in further detail below. The guide <b>15</b> has a bore <b>17</b> that can slide over a stylet. The main shell <b>12</b> houses four deployable ratcheting locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>adapted and configured to engage adjacent vertebral portions of the spinous process. The shell <b>12</b> has four openings <b>46</b><i>a</i>-<b>46</b><i>d </i>that allow the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>to extend outward from the shell <b>12</b>. The locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are preferably formed from a lightweight, high-strength biocompatible material, such as, for example, titanium or a similar material.

During deployment of the implant <b>10</b>, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are stowed within the shell <b>12</b> of the implant <b>10</b>, as best seen in <figref idrefs="DRAWINGS">FIGS. 10A and 11</figref>, forming a streamlined structure. As best seen in <figref idrefs="DRAWINGS">FIGS. 4</figref>, <b>5</b>A, <b>5</b>B, <b>6</b>A, <b>6</b>B, <b>10</b>A and <b>10</b>B, two curved guide tracks <b>19</b> formed within the shell portions <b>12</b><i>a</i>, <b>12</b><i>b </i>accommodate the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>in the stowed position.

Each locking wing <b>14</b><i>a</i>-<b>14</b><i>d </i>includes a set of ratchet teeth <b>16</b>, as best seen in <figref idrefs="DRAWINGS">FIGS. 7A-7C</figref>. The ratchet teeth <b>16</b> on each wing <b>14</b><i>a</i>-<b>14</b><i>d </i>are dimensioned and configured to engage a corresponding pawl structure <b>18</b> formed adjacent the openings <b>46</b><i>a</i>-<b>46</b><i>d </i>on the shell <b>12</b> during deployment, so as to lock the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>in the desired position. The locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>fixate the adjacent spinous processes. While the implant <b>10</b> is used primarily as a spacer between spinous processes, the selectively deployable wings <b>14</b><i>a</i>-<b>14</b><i>d </i>enable the implant <b>10</b> to be used to distract the spinous process as well. Advantageously, once the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are deployed to fixate the spinous processes, migration of the implant <b>10</b> is prevented.

As best seen in <figref idrefs="DRAWINGS">FIG. 3</figref>, the two wings <b>14</b><i>c </i>and <b>14</b><i>b </i>on the side of the implant <b>10</b> are located on parallel, spaced apart geometric planes that extend on the side of the horizontal centerline of the implant shell <b>12</b>. In other words, in a deployed position, locking wing <b>14</b><i>b </i>resides in a deployment plane that is parallel to the deployment plane of locking wing <b>14</b><i>c</i>. Similarly, locking wing <b>14</b><i>a </i>resides in a plane that is parallel to the deployment plane of locking wing <b>14</b><i>d</i>. It follows that, locking wings <b>14</b><i>a </i>and <b>14</b><i>c </i>reside in a common deployment plane, and locking wings <b>14</b><i>b </i>and <b>14</b><i>d </i>reside in a common deployment plane. This orientation helps to prevent migration of the device and maintain stability within the spinous process.

The movement or deployment of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>is controlled or otherwise effectuated by a pair of coaxial locking wheels <b>20</b><i>a </i>and <b>20</b><i>b</i>, shown in FIGS. <b>4</b> and <b>8</b>A-<b>8</b>D. The locking wheels <b>20</b><i>a </i>and <b>20</b><i>b </i>have a central opening <b>25</b><i>a </i>and <b>25</b><i>b</i>, respectively, for mounting on a central hub <b>21</b> in the shell <b>12</b>. Locking wheel <b>20</b><i>a </i>nestles in upper shell portion <b>12</b><i>a </i>to control the movement of wings <b>14</b><i>a </i>and <b>14</b><i>c</i>, while locking wheel <b>20</b><i>b </i>nestles in lower shell portion <b>12</b><i>b </i>to control the movement of wings <b>14</b><i>b </i>and <b>14</b><i>d</i>. More particularly, each of the opposed ends <b>23</b><i>a</i>, <b>23</b><i>b </i>of locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>are adapted and configured to exert a force against a bearing surface <b>22</b> formed at the end of each locking wing <b>14</b><i>a</i>-<b>14</b><i>d</i>, which is best seen in <figref idrefs="DRAWINGS">FIGS. 10A and 10B</figref>.

In accordance with a preferred embodiment of the subject invention, the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>and thus the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are controlled by a deployment cable <b>27</b>, shown in <figref idrefs="DRAWINGS">FIG. 10B</figref>. One or more cables may be employed. The deployment cable <b>27</b> attaches to a key-shaped opening <b>41</b> formed in the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>to facilitate remote actuation of the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>and corresponding movement of the ratcheting locking wings <b>14</b><i>a</i>, <b>14</b><i>b</i>. The cable <b>27</b> splits on the distal end and terminates in two balls (not shown). Each ball can pass through the respective key-shaped opening <b>41</b> and be selectively captured therein. The cable <b>27</b> passes out of the shell <b>12</b> via a passage <b>90</b> for use by the surgeon. Once deployed, the cable <b>27</b> may be disengaged from the key-shaped opening <b>41</b> or cut as described below.

Alternatively, the key-shaped opening <b>41</b> may be located further from the pivot point of the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>to provide a greater mechanical advantage. The cable <b>27</b> may also form a loop by attaching to the two key-shaped openings <b>41</b>. The loop may be a simple loop at the distal end of the cable <b>27</b> or a long loop that passes out of the shell via passage <b>90</b>. Additionally, a similar second loop of cable (not shown) might attach to two other key-shaped openings on the opposite ends of the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>to further increase the mechanical force during deployment. The second loop of cable would also pass out of the implant <b>10</b> through a passage similar to passage <b>90</b> but formed in the distal end of the implant <b>10</b>. Once deployed, the cable loop may either be cut or left as part of the implant <b>10</b>.

As best seen in <figref idrefs="DRAWINGS">FIGS. 1-3</figref>, <b>9</b>A-<b>9</b>D and <b>11</b>, the interspinous implant <b>10</b> is associated with a placement tool <b>24</b> adapted and configured to facilitate the percutaneous introduction of the implant <b>10</b>. Placement tool <b>24</b> includes an elongated tubular stem <b>26</b> having a straightened distal portion <b>26</b><i>a </i>and a curved proximal portion <b>26</b><i>b</i>. In another embodiment, the tubular stem <b>26</b> may be curved without a straightened portion. The tubular stem <b>26</b> has a central lumen <b>29</b> for accommodating the proximal portion of the deployment cable <b>27</b>. At a distal end, the placement tool <b>24</b> has a coupling sleeve <b>28</b> for selectively engaging a locking cuff <b>49</b> on a tail <b>10</b><i>b </i>of the shell <b>12</b>. The sleeve <b>28</b> has a slot <b>92</b> and the cuff <b>49</b> has one or more protrusions <b>94</b> that engage to form a twist lock to selectively couple the placement tool <b>24</b> to the shell <b>12</b>. The sleeve <b>28</b> may also form a cutting surface <b>51</b>, as best seen in <figref idrefs="DRAWINGS">FIGS. 10A and 10B</figref>, against which the cable <b>27</b> may be routed for cutting. As the sleeve <b>28</b> rotates, a protrusion <b>59</b> lifts the cable <b>27</b> so that the cutting surface <b>51</b> can sever the cable <b>27</b> after the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>have been deployed by the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b</i>. When the cable <b>27</b> is a long loop, one end is simply released while the other end of the cable <b>27</b> is pulled to remove the cable <b>27</b>. It is also envisioned that each locking wheel <b>20</b><i>a</i>, <b>20</b><i>b </i>may have a loop or respective cable <b>27</b>. In still another embodiment, the cable <b>27</b> is relatively short and remains attached to the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>after deployment. To actuate the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b</i>, there is a secondary longer cable (not shown) that passes from the proximal to the distal end of the placement tool <b>24</b> and loops around the cable <b>27</b>. The secondary cable then passes back out of the proximal end of the placement tool <b>24</b>. The ends of the secondary cable are pulled in order to pull cable <b>27</b> and, in turn, actuate the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b</i>. Then, one end of the secondary cable is simply released, while the other end is pulled to remove the secondary cable.

Referring to <figref idrefs="DRAWINGS">FIG. 8E</figref>, another embodiment of a locking wheel <b>20</b>′ is shown. The locking wheel <b>20</b>′ has spaced grooves located on the central hub <b>21</b>′ adapted and configured to engage complementary spaced teeth on an actuating mechanism <b>27</b>′. The central hub <b>21</b>′ is relatively thicker near the central opening <b>25</b>′ so that the teeth on the conical head of the actuating mechanism <b>27</b>′ effectively interdigitate with the grooves to form a gear drive mechanism. Various other shapes could also form an effective gear drive mechanism. The actuating mechanism <b>27</b>′ is preferably a rod that extends along the long axis of the implant <b>10</b>. The conical head of the actuating device <b>27</b>′ may be between the two locking wheels <b>20</b>′ or each locking wheel may have a respective actuating mechanism <b>27</b>′. On the other end (not shown), the actuating mechanism <b>27</b>′ terminates near the end of the shell <b>12</b> and forms a slot. A screwdriver type of device (not shown) would insert down the placement tool <b>24</b> and couple to the rod slot. By turning the screwdriver type device, the actuating mechanism <b>27</b>′ would turn and, thereby, one or both of the locking wheels <b>20</b>′ would turn in opposite direction to accomplish deployment of the locking wings <b>14</b><i>a</i>, <b>14</b><i>b </i>of the implant <b>10</b>.

Stylet Assembly

Referring now to <figref idrefs="DRAWINGS">FIG. 12</figref>, there is shown a stylet assembly <b>30</b> adapted and configured to facilitate the percutaneous insertion of the interspinous implant <b>10</b>. The stylet assembly <b>30</b> includes an elongated graduated positioning stylet <b>32</b> for setting the position of the assembly <b>30</b> over the central axis of the patient's spine. On a distal end, the graduated positioning stylet <b>32</b> has a pointed tip <b>31</b> adapted and configured to be inserted in the patient. On a proximal end, the graduated positioning stylet <b>32</b> has a knob <b>37</b> to allow a surgeon to more easily control the stylet <b>32</b>. The stylet assembly <b>30</b> further includes a curved stylet <b>34</b> for gaining lateral access to the interspinous space and an adjustable guide bridge <b>36</b> having a curved guide sleeve <b>36</b><i>a </i>for the curved stylet <b>34</b>. The adjustable guide bridge <b>36</b> also has a central portion <b>36</b><i>b </i>to act as an insertion guide for the graduated positioning stylet <b>32</b>. The curved stylet <b>34</b> has a distal end <b>33</b> adapted and configured to be inserted in the patient and a proximal end with a handle/travel stop <b>34</b><i>a</i>. The relationship between the handle/travel stop <b>34</b><i>a </i>and curved guide sleeve <b>36</b><i>a </i>sets a maximum insertion depth of the curved stylet <b>34</b>.

Unilateral Placement of the Implant

Referring to <figref idrefs="DRAWINGS">FIG. 13</figref>, in use the graduated stylet <b>32</b> is advanced through a small percutaneous incision in the patient's back, under fluoroscopy, so that the pointed tip <b>31</b> reaches to the interspinous space. The distance (D) from the skin to the interspinous space is then noted, based on graduations on the stylet <b>32</b>. Alternatively, the same distance can be measured from a pre-operative CT scan. In each event, the center guide sleeve <b>36</b><i>b </i>of the adjustable guide bridge <b>36</b> is positioned over stylet <b>32</b>, and the distance (D) is marked off in a direction perpendicular to the length of the spine. This distance (D) corresponds to the adjusted length of the adjustable guide bridge <b>36</b> of stylet assembly <b>30</b>. Thereafter, the curved stylet <b>34</b> is advanced down to the interspinous space through the curved guide sleeve <b>36</b><i>a </i>of the adjustable guide bridge <b>36</b>. The curved stylet <b>34</b> has a radius of curvature equal to D so that upon insertion, the distal end <b>33</b> moves adjacent the pointed tip <b>31</b> of the graduated stylet <b>32</b> at the interspinous space. At this point of advancement of the curved stylet <b>34</b>, the travel stop <b>34</b><i>a </i>at the end of the stylet <b>34</b> abuts the guide sleeve <b>36</b><i>a </i>to prevent further extension. Thereupon, the travel stop <b>34</b><i>a </i>is threadably or otherwise removed from the end of the curved stylet <b>34</b>, and the remainder of the stylet assembly <b>30</b> including the graduated stylet <b>32</b> are removed as well. However, the curved stylet <b>34</b> remains in place as shown in <figref idrefs="DRAWINGS">FIG. 14</figref>.

Then, as shown in <figref idrefs="DRAWINGS">FIGS. 14 and 15</figref>, successive dilators <b>40</b>, <b>42</b> are placed over the curved stylet <b>34</b>, while observing the interspinous space under fluoroscopy. The dilators <b>40</b>, <b>42</b> also may have radii of curvature equal to D. The dilators <b>40</b>, <b>42</b> serve to distract the interspinous space. Although two dilators <b>40</b>, <b>42</b> are shown, more or less could be utilized to accomplish the desired distraction of the interspinous space. Once the adequate distraction of the interspinous space is observed, the implant <b>10</b> is percutaneously inserted through a lumen <b>43</b> formed in the last dilator <b>42</b>. Preferably, the dilators <b>40</b>, <b>42</b> distract the spinous processed and the implant <b>10</b> only maintains the distraction although the implant <b>10</b> may also perform distraction. Alternatively, the deployment of the implant <b>10</b> may be done by threading the implant <b>10</b> over the curved stylet <b>34</b> as a guide into the interspinous space by way of the guide bore <b>15</b> on the lower shell portion <b>12</b><i>b. </i>

The implant <b>10</b> is maneuvered down to the interspinous space. As shown in <figref idrefs="DRAWINGS">FIG. 16</figref>, the implant <b>10</b> has a knob <b>39</b> selectively attached to the placement tool <b>24</b> to help the physician maneuver the implant <b>10</b>. The knob <b>39</b> may include an extension that inserts into the central lumen <b>29</b> in order to make the stem <b>26</b> more rigid. Once the implant <b>10</b> is in position, the dilator <b>42</b> may be removed, while maintaining the position of the implant <b>10</b> for subsequent deployment of the locking wings <b>14</b><i>a</i>-<b>14</b><i>b. </i>

Actuating the Locking Wings after Unilateral Insertion

Once the shell <b>12</b> is nestled between the spinous processes so that contact is made with the bone at the depressions <b>13</b>, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are deployed. The surgeon utilizes the cable <b>27</b> to deploy the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>and, thereby, fix the position of the implant <b>10</b>. The distal end <b>27</b><i>a</i>, <b>27</b><i>b </i>of the cable <b>27</b> is attached to the coaxial locking wheels <b>20</b><i>a</i>, <b>20</b><i>b</i>, respectively, so that as the cable <b>27</b> is pulled proximally, the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>rotate about the central hub <b>21</b> in the shell <b>12</b>.

The opposing ends <b>23</b><i>a</i>, <b>23</b><i>b </i>of the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>push against the bearing surfaces <b>22</b> of the respective locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>so that the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are urged outward in the guide tracks <b>19</b> of the shell <b>12</b>. As the ratchet teeth <b>16</b> of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>move outward past the pawl structure <b>18</b> of the shell <b>12</b>, the pawl <b>18</b> engages the corresponding ratchet tooth <b>16</b> to prevent the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>from moving inward back into the shell <b>12</b>. As a result of the outward movement, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>engage the spinous processes until the surgeon feels adequate resistance, e.g., deployment. Once the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are deployed, the cable <b>27</b> is released or cut. The implant <b>10</b> then remains deployed between the spinous processes. In one embodiment, a biasing element or elements such as a spring extends between the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>so that movement thereof does not occur before or after deployment.

In one embodiment, to release the cable <b>27</b>, a second cable (not shown) extends down the placement tool <b>24</b>. The second cable loops around the cable <b>27</b> and returns through the central lumen <b>29</b> of the placement tool <b>24</b>. The surgeon can pull on the second cable to effect a pull on cable <b>27</b>. Once the locking wings are deployed, the surgeon releases one end of the second cable loop, and then pulls this second cable out of the placement tool <b>24</b>, thus leaving cable <b>27</b> with the implant in the patient.

Bilateral Placement of the Implant

Referring to <figref idrefs="DRAWINGS">FIGS. 17-21</figref>, there are illustrated the operative steps used in the bilateral placement of the interspinous implant <b>10</b> of the subject invention. First, as shown in <figref idrefs="DRAWINGS">FIG. 17</figref>, the central portion <b>36</b><i>b </i>of the adjustable guide bridge <b>36</b> is positioned over the graduated stylet <b>32</b>, and the graduated stylet <b>32</b> is inserted to the depth of the patient's spine. The measured distance (D) is used to size the adjustable guide bridge <b>36</b>. A second curved stylet <b>34</b>′, similar to curved stylet <b>34</b> but longer, is then advanced through the skin down to the interspinous space through the curved guide sleeve <b>36</b><i>a </i>of the adjustable guide bridge <b>36</b>. The curved stylet <b>34</b>′ is also extendable, and the advancement of the curved stylet <b>34</b>′ continues until the distal end <b>33</b> of the curved stylet <b>34</b>′ punctures the skin on the opposite side of the spine.

As shown in <figref idrefs="DRAWINGS">FIGS. 18 and 19</figref>, the adjustable guide bridge <b>36</b> and graduated stylet <b>32</b> are removed. Successive tubular dilators <b>50</b>, <b>52</b> are placed over the curved stylet <b>34</b>′ while observing the interspinous space under fluoroscopy. These dilators <b>50</b>, <b>52</b>, with successively larger diameters, are along the same route as the curved stylet <b>34</b>′ through the interspinous space until distal ends <b>53</b>, <b>55</b> respectively, pass out of the patient's body.

Once adequate distraction of the interspinous space is observed, the interspinous implant <b>10</b>, with a profile slightly less than the diameter of the larger dilator <b>52</b>, is percutaneously inserted through the lumen <b>57</b> of the last dilator <b>55</b>. The surgeon guides the implant <b>10</b> down to the interspinous space, approaching from either or both sides of the spine, as shown in <figref idrefs="DRAWINGS">FIG. 20</figref>. Alternatively, once the interspinous space has been adequately distracted by the dilators <b>50</b>, <b>52</b>, a stylet guide (not shown) could again be inserted after removal of the last dilator <b>52</b>. The implant <b>10</b> could then be inserted over the stylet guide into the interspinous space.

Actuating the Locking Wings after Bilateral Insertion

As best seen in <figref idrefs="DRAWINGS">FIG. 20</figref>, to actuate the locking wings <b>14</b><i>a</i>-<b>14</b><i>d</i>, the implant is inserted through the final dilator <b>52</b> using the placement tool <b>24</b><i>a </i>attached to the proximal tail <b>10</b><i>b </i>of the implant <b>10</b>. By passing a second placement tool <b>24</b><i>b </i>into the dilator <b>52</b> in an opposing direction, the second placement tool <b>24</b><i>b </i>attaches to a distal nose <b>10</b><i>a </i>of the implant <b>10</b>. Each placement tool <b>24</b><i>a</i>, <b>24</b><i>b </i>has a corresponding knob <b>39</b><i>a</i>, <b>39</b><i>a </i>on the proximal end. The final dilator <b>52</b> is fully or partially removed while maintaining the position of the implant <b>10</b> with the placement tool <b>24</b><i>a </i>or tools <b>24</b><i>a</i>, <b>24</b><i>b</i>, as the case may be.

While holding the implant <b>10</b> in position with the placement tools <b>24</b><i>a</i>, <b>24</b><i>b</i>, the deployment cable (not shown) is pulled to actuate the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>of implant <b>10</b>. A distal end of the cable is attached to the coaxial locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>so that as the cable is pulled, the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>rotate about the central hub <b>21</b> in the shell <b>12</b>. The opposing ends <b>23</b><i>a</i>, <b>23</b><i>b </i>of the locking wheels <b>20</b><i>a</i>, <b>20</b><i>b </i>push against the bearing surfaces <b>22</b> of the respective locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>so that the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>slide outward in the guide tracks <b>19</b> of the shell <b>12</b>. As the ratchet teeth <b>16</b> of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>move outward past the pawl structure <b>18</b> of the shell, the pawl <b>18</b> engages the corresponding ratchet tooth <b>16</b> to prevent the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>from moving inward back into the shell <b>12</b>. As a result of the outward movement, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>engage the spinous processes until the surgeon feels adequate resistance, e.g., deployment as shown in <figref idrefs="DRAWINGS">FIG. 21</figref>.

Once the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are deployed, the cable is released and the placement tools <b>24</b><i>a</i>, <b>24</b><i>b </i>are detached from the nose <b>10</b><i>a </i>and tail <b>10</b><i>b </i>of the implant <b>10</b>. The implant <b>10</b> then remains deployed between the spinous processes, as shown in <figref idrefs="DRAWINGS">FIG. 21</figref>. Before fully detaching the placement tool <b>24</b><i>a </i>from the implant <b>10</b>, the deployment cable is cut. To cut the cable, the placement tool <b>24</b><i>a </i>rotates the cutting surface <b>51</b> and, in turn, the cable is severed by being routed against the cutting surface <b>51</b>.

It is envisioned that the placement tools <b>24</b><i>a</i>, <b>24</b><i>b </i>each attach to the interspinous implant <b>10</b> through a selective twist lock as noted above. Alternatively, the placement tools <b>24</b><i>a</i>, <b>24</b><i>b </i>could be designed to also have tapered ends with prongs that attach to a bulbous portion of the nose <b>10</b><i>a </i>and tail <b>10</b><i>b </i>of the interspinous implant <b>10</b>. Similarly, an unlocking rod could be inserted into the placement tools <b>24</b><i>a</i>, <b>24</b><i>b </i>or dilator <b>52</b> to disengage them from the shell <b>12</b>.

Alternative Control Device

Referring now to <figref idrefs="DRAWINGS">FIGS. 22 and 23</figref>, a control device <b>60</b> is shown. The control device <b>60</b> may be used to actuate the cable(s) <b>27</b> or to place the implant <b>10</b>. Accordingly, the size and shape may vary significantly from that shown because the principle of operation is widely applicable. The control device <b>60</b> has an arcuate tube <b>61</b>. Preferably, the arcuate tube <b>61</b> has a radius of curvature of D.

The control device <b>60</b> may be used to actuate the cable <b>27</b> so that cutting is not required by detaching from the cable <b>27</b> after deployment. For example, the arcuate tube <b>61</b> has a tapered distal end <b>62</b>. The tapered end <b>62</b> has radially inwardly extending flexible prongs <b>64</b> with longitudinal slots <b>66</b> in between. The prongs <b>64</b> form a distal opening <b>68</b>. It is envisioned that the proximal end of the deployment cable <b>27</b> would be attached to a small ball (not shown) on the proximal end of the cable <b>27</b>. The ball would have a diameter slightly greater than the opening <b>68</b> so that the ball is captured in the tapered distal end <b>62</b>. In particular, the flexible prongs <b>64</b> of the cable attachment device <b>60</b> capture the cable ball. By capturing the cable ball, the control device <b>60</b> can be used to pull the cable <b>27</b> by pulling the device <b>60</b>.

Once the cable <b>27</b> has been pulled, with the deployment of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>of the implant <b>10</b>, the ball of the cable <b>27</b> is released from the tapered distal end <b>62</b> of the arcuate tube <b>61</b>. Release of the ball from the control device <b>60</b> is accomplished by inserting a second tube <b>67</b> into the arcuate tube <b>61</b>, as shown in <figref idrefs="DRAWINGS">FIG. 22</figref>. The second tube <b>67</b> would have a slightly smaller diameter than the arcuate tube <b>61</b>. The tube <b>67</b> provides adequate force to deflect the prongs <b>64</b> resulting in an increase in diameter of the opening <b>68</b> and, in turn, release of the ball on the end of the deployment cable <b>27</b>. Thus, a predetermined, short amount of cable <b>27</b> may be left implanted.

It is also envisioned that the implant <b>10</b> could be designed so that deployment of the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>is accomplished from the nose <b>10</b><i>a </i>and tail <b>10</b><i>b </i>of the shell <b>12</b>, bilaterally, whereby two separate cables could be used to deploy the wings <b>14</b><i>a</i>-<b>14</b><i>d</i>, doubling the mechanical advantage provided during a unilateral approach using a single deployment cable <b>27</b>. The control device <b>60</b> may be used with one or both such cables.

In another embodiment, the control device <b>60</b> is used to place the implant <b>10</b>. The flexible prongs <b>64</b> would attach to indentations on the implant <b>10</b>. Two control devices <b>60</b> could be used with one attaching to each end of the implant <b>10</b>. Thus, the arcuate tubes <b>61</b> could be used to position the implant <b>10</b>. Upon deployment of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d</i>, second tubes <b>67</b> would be used to release the control devices <b>60</b> from the implant <b>10</b>.

Using the Locking Wings to Distract

In an alternative approach, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are used to distract the spinous process. Rather than inserting increasing diameter dilators, the implant <b>10</b> is put in position. Then, the cable <b>27</b> is used to not only deploy the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>but the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are also sized and configured to engage and distract the spinous process. For example, each locking wing <b>14</b><i>a</i>-<b>14</b><i>d </i>may have a hook shaped protrusion positioned to distract the spine as the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are deployed.

Implant in Deployed Position

Once deployed, the interspinous implant <b>10</b> of the subject invention is attached to the adjacent spinous processes. The implant <b>10</b> provides restriction of movement of the spine in both extension as well as flexion. With slight modification of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d</i>, however, the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>could alternatively be designed to simply abut the spinous processes, and thereby the implant <b>10</b> could allow flexion of the spine.

It is also envisioned that the implant <b>10</b> can permanently engage the spinous processes. For example, the tips of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>can be sharp to create penetration of the spinous processes. The tips of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>could be modified so that the edge that forms a point on opposing claws so that the opposing wings could penetrate deeper or through the spinous process bones. Further, the direction of the points on the opposing claws could be reversed. Additionally, the tips of the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>could have one or more barbs to prevent disengagement. Still further, the tips of the wings <b>14</b><i>a</i>-<b>14</b><i>d </i>could have perforations that allow for bony in-growth from the spinous processes. In addition to being offset, preferably, the curves of the locking wings <b>14</b><i>a</i>-<b>14</b><i>d </i>are slightly different to allow the opposing claims not to meet so that each can penetrate deeper through the bone.

Predetermining a Size of the Implant

Referring now to <figref idrefs="DRAWINGS">FIGS. 24 and 25</figref>, there is shown an apparatus <b>100</b> and a method for measuring percutaneously the optimum size of an interspinous implant <b>10</b>, which can range from about 8 mm in diameter to about 14 mm in diameter, depending upon the anatomy of the patient and the location of the implant <b>10</b> in the spinous process. Those skilled in the art will readily appreciate that the interspinous measurement devices disclosed herein can also be used to measure or otherwise determine an optimum degree of force for interspinous distraction.

Referring to <figref idrefs="DRAWINGS">FIG. 24</figref>, the measurement apparatus <b>100</b> is shown in a closed position, as the measurement apparatus <b>100</b> is percutaneously introduced into the interspinous space. The apparatus <b>100</b> includes a proximal deployment portion <b>110</b> that includes a plunger tube <b>102</b> carrying a rod <b>104</b>. The rod <b>104</b> extends approximately flush with at the distal end <b>106</b> of the plunger tube <b>102</b>.

The apparatus <b>100</b> further includes a distal measuring assembly <b>112</b>, which consists of four connected arms <b>114</b><i>a</i>-<b>114</b><i>d</i>. The connected arms <b>114</b><i>a</i>-<b>114</b><i>d </i>are pivotally connected at four coupling joints <b>115</b><i>a</i>-<b>115</b><i>d</i>. The rod <b>104</b> of the plunger tube <b>102</b> extends on the distal end to connect to the coupling joint <b>115</b><i>c</i>. Adjacent the coupling joints <b>115</b><i>b</i>, <b>115</b><i>d</i>, there are two opposed concave cradles <b>116</b><i>a</i>, <b>116</b><i>b </i>are adapted and configured to cup the adjacent spinous processes.

To measure percutaneously the optimum size of an interspinous implant <b>10</b>, the apparatus <b>100</b> is placed so that the opposed concave cradles <b>116</b><i>a</i>, <b>116</b><i>b </i>are between adjacent spinous processes. The rod <b>104</b> is held stationary while the plunger tube <b>102</b> is pushed in a distal direction. The connected arms <b>114</b><i>a</i>-<b>114</b><i>d </i>are driven to expand into a trapezoidal shape as shown by movement arrows “a” in <figref idrefs="DRAWINGS">FIG. 25</figref>). The expansion of the connected arms <b>114</b><i>a</i>-<b>114</b><i>d </i>may cause the spinous processes to be distracted if not already done so by dilators. A measurement of the travel distance of rod <b>104</b> within in the tube <b>102</b> will correlate to the length to which the interspinous space was distracted, i.e., the size of the trapezoidal shape. Thus, the travel distance of the rod <b>104</b> can be used to determine the appropriate size of the interspinous implant <b>10</b>. To facilitate measuring the travel distance, the rod <b>104</b> may have graduations or markings that correspond to an actual measurement or otherwise identify the appropriate size selection of the implant <b>10</b>.

To measure the optimum degree of force for interspinous distraction, the plunger tube <b>102</b> and/or rod <b>104</b> are operatively associated with a strain gauge (not shown). Appropriate laboratory testing could be done to determine the optimal degree of distractive force so that the apparatus <b>100</b> is calibrated. The calibrated apparatus <b>100</b> could then be utilized to determine the appropriate implant <b>10</b> to apply that optimal force. To calibrate the apparatus <b>100</b>, a clinical study could be performed where the amount of distractive force is correlated with radiological studies showing the degree of distraction. Further, clinical studies could be performed looking at long term clinical results, as well as possible subsidence of the implant <b>10</b> into the spinous processes, with different degrees of force exerted.

Referring to <figref idrefs="DRAWINGS">FIGS. 26 and 27</figref>, there is illustrated another device <b>200</b> for measuring percutaneously the optimum size of interspinous implant <b>10</b> in the closed and open positions, respectively. The measuring device <b>200</b> includes an elongated body portion <b>210</b> having a pair of jaw members <b>212</b><i>a</i>, <b>212</b><i>b </i>at the distal end thereof for positioning in the interspinous space. The jaw members <b>212</b><i>a</i>, <b>212</b><i>b </i>have respective cradles <b>214</b><i>a</i>, <b>214</b><i>b </i>adapted and configured to cup the adjacent spinous processes.

Movement of the jaw members from the closed position of <figref idrefs="DRAWINGS">FIG. 26</figref> to the open or measuring position of <figref idrefs="DRAWINGS">FIG. 27</figref> is controlled in a conventional manner (e.g., by oppositely angled cam slots or the like) by way of a flexible rod <b>216</b> that extends through the body portion <b>210</b>, for example, similarly to plunger tube and rod as shown in <figref idrefs="DRAWINGS">FIGS. 24 and 25</figref>. Again, a measurement of the travel distance of the rod <b>216</b> within the body portion <b>210</b> may correlate to the length to which the interspinous space was distracted or even directly to the size of the appropriate implant <b>10</b>. Further, a strain gauge may be used, for example by coupling the strain gauge to the plunger tube <b>102</b> or rod <b>216</b>, to determine a preferable amount of force to apply.

It is also envisioned and within the scope of the subject disclosure that a temporary balloon can be inserted into the interspinous space to determine the appropriate size of implant <b>10</b> to be used. Additionally, an optimum force required for interspinous distraction could be correlated with the amount of pressure required to blow up the balloon. Thus, the size of the implant and the optimum force would be determined by how much the balloon was inflated to obtain that optimum pressure.

A Tool Kit for Percutaneous Placement the Implant

Referring to <figref idrefs="DRAWINGS">FIG. 28</figref>, a tool kit <b>400</b> for facilitating the percutaneous implantation of the implant <b>10</b> is shown. The tool kit <b>400</b> would preferably include an enclosure <b>410</b> containing, among other things, a stylet assembly <b>30</b>, which includes the elongated graduated positioning stylet <b>32</b>, the curved stylet <b>34</b> and the adjustable bridging portion <b>36</b> with curved guide sleeve <b>36</b><i>a</i>. It is envisioned that the tool kit <b>400</b> would include either a curved stylet <b>34</b> configured for a unilateral approach to the spinous process (see <figref idrefs="DRAWINGS">FIG. 13</figref>), or a curved stylet <b>34</b>′ adapted and configured for a bilateral approach to the spinous process (see <figref idrefs="DRAWINGS">FIG. 18</figref>), or it could include both types of curved stylets.

The tool kit <b>400</b> may also include one or more implants <b>10</b> of varying sizes. In addition, the tool kit <b>400</b> preferably includes a set of tubular dilators (e.g., dilators <b>42</b>, <b>50</b>, <b>52</b>) of varying diameter that correspond to the varying implants <b>10</b>. The dilators may have two different lengths depending upon whether the dilators <b>42</b>, <b>50</b>, <b>52</b> are used in a bilateral approach procedure or a unilateral approach procedure. It is envisioned that the tubular dilators <b>42</b>, <b>50</b>, <b>52</b> could range from about 8 mm or less up to about 14 mm or greater. The dilators, curved stylet, and the placement tools would also have different radii of curvature to accommodate the body shape of different patients. Of course, the implants could be packaged separately for use with an insertion kit sized by the radius of curvature of the dilators, curved stylet, and the placement tools.

While the apparatus and methods of subject invention have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and cope of the subject invention.